Note that the data for comparing the different nanodiscs were acquired on the same setup at the same time.
In order to establish the repeatability of these measurement, repeated measurements of the reference nanodisc (MSP1D1, DMPC) were performed later on a different setup.
The absolute values for the contrast are therefore different, due to the use of a partial reflector of different transmissivity, and to establish repeatability they can be normalised by the mean across all measurements.